Multiple variable valve lift apparatus

ABSTRACT

A multiple variable valve lift apparatus connected with a valve opening and closing unit which is adapted to rolling-contact one end thereof with a cam and is operated to open or close by a rotation of the cam, and operating to select the cam which is rolling-contacted with the valve opening and closing unit for changing a valve lift, may include a normal cam rolling-contacting with the valve opening and closing unit so as to realize a normal lift of a predetermined valve, and a low cam rolling-contacting with the valve opening and closing unit so as to realize a valve lift which is lower and longer than the normal lift realized by the normal cam, wherein the normal cam or the low cam is selectively rolling-contacted to the valve opening/closing unit according to a driving state.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2013-0107885 filed on Sep. 9, 2013, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multiple variable valve lift apparatus. More particularly, the present invention relates to a multiple variable valve lift apparatus for improving fuel consumption.

2. Description of the Related Art

Generally, an internal combustion engine receives fuel and air into a combustion chamber and generates power by combusting the fuel and the air. Herein, an intake valve is operated by drive of a camshaft, and air flows into the combustion chamber during when the intake valve is open. In addition, an exhaust valve is operated by drive of a camshaft, and air is exhausted from the combustion chamber while the exhaust valve is open.

Optimal operations of the intake valve or the exhaust valve are determined according to rotation speed of the engine. That is, lift and open/close timing of the valves are properly controlled according to rotation speed of the engine. A plurality of cams may be disposed at a camshaft such that a valve is operated by various lift for realizing suitable valve operation according to rotation speed of an engine.

In case that the plurality of cams are provided so as to drive the valve by various lift, the valve lift is changed as a cam portion forming the plurality of cams is moved along an axial direction of the camshaft such that one cam realizing the valve lift is selected according to situation.

Meanwhile, changing of the valve lift may be performed for changing open/close time of a valve as well as to select high or low of the valve lift.

However, if size of a cam lobe is entirely larger for increasing open time of a valve even though the high lift is not required, the valve lift is increased. In addition, mechanical friction is increased according to the valve lift is increased such that fuel consumption may be deteriorated.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

SUMMARY OF THE INVENTION

Various aspects of the present invention are directed to providing a multiple variable valve lift apparatus having advantages of simultaneously improving fuel consumption and NVH (noise vibration harness) performance.

In an aspect of the present invention, a multiple variable valve lift apparatus connected with a valve opening and closing unit which is adapted to rolling-contact one end thereof with a cam and is operated to open or close by a rotation of the cam, and operating to select the cam which is rolling-contacted with the valve opening and closing unit for changing a valve lift, may include a normal cam rolling-contacting with the valve opening and closing unit so as to realize a normal lift of a predetermined valve, and a low cam rolling-contacting with the valve opening and closing unit so as to realize a valve lift which is lower and longer than the normal lift realized by the normal cam, wherein the normal cam or the low cam is selectively rolling-contacted to the valve opening/closing unit according to a driving state.

The valve is early opened and is lately closed to compare with the normal lift in the valve lift realized by the low cam.

The normal lift realized by that the normal cam is rolling-contacted with the valve opening and closing unit is a predetermined valve lift such that efficiency of an engine is improved when a vehicle is driven at a high speed and a normal speed.

The low cam realizes the valve lift by rolling-contacting with the valve opening and closing unit such that efficiency of an engine is improved when a vehicle is driven at a low speed.

The methods and apparatuses of the present invention may have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a multiple variable valve lift apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a perspective view of a cam portion according to an exemplary embodiment of the present invention.

FIG. 3 is a graph showing valve lift by a normal cam and a LIVC cam according to an exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a multiple variable valve lift apparatus according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a multiple variable valve lift apparatus 1 according to an exemplary embodiment of the present invention includes a camshaft 100, cam portions 40 and 60, a solenoid 10, an operating unit 30 and 50, an interlock unit 70, and a pin operating unit 20. Herein, the operating unit 30 and 50 and interlock unit 70 compose an operating portion which operates for changing valve lift, and the solenoid 10 and the pin operating unit 20 compose a control portion which controls the operation of the operating unit 30 and 50 and interlock unit 70.

The camshaft 100 is a shaft which is rotated by rotation of a crankshaft of an engine. The camshaft 100 is well-known to a person of ordinary skill in the art such that a detailed description thereof will be omitted.

The cam portion 40 and 60 is a portion that a cam 41, 42, 48, 49, 61, 62, 68, and 69 for operating an intake valve or an exhaust valve of an engine is formed, and is formed in a hollow cylinder shape having uniform thickness. In addition, the camshaft 100 is inserted into the hollow of the cam portion 40 and 60. Thus, an entire shape of the cam portion 40 and 60 and the camshaft 100 is to be a shape that the cam portion 40 and 60 is protruded from an exterior circumference of the camshaft 100. Herein, the hollow of the cam portion 40 and 60 is formed in a circle shape corresponding to an external circumference of the camshaft 100. That is, an interior circumference of the cam portion 40 and 60 is contacted to an exterior circumference of the camshaft 100. Furthermore, an interior circumference of the cam portion 40 and 60 is slid on an exterior circumference of the camshaft 100 such that the cam portion 40 and 60 is moved along an axial direction of the camshaft 100. Meanwhile, the cam portion 40 and 60 is disposed to rotate together with the camshaft 100. The composition that the cam portion 40 and 60 is movable along an axial direction of the camshaft 100, and the cam portion 40 and 60 and the camshaft 10 are coupled with each other such that the cam portion 40 and 60 and the camshaft 100 are rotated together can be realized by types such as the spline according to design of a person of ordinary skill in the art.

The cam portion 40 and 60 includes two cam portions 40 and 60 which are a first cam portion 40 and a second cam portion 60. Herein, the first cam portion 40 is adapted to operate a valve disposed at one cylinder, and the second cam portion 60 is adapted to operate a valve disposed at another cylinder. Further, the first cam portion 40 can be provided for two valves disposed at one cylinder, and the second cam portion 60 can be provided for two valves disposed another cylinder.

In FIG. 1, a multiple variable valve lift apparatus 1 which is adapted to operate a valve at two cylinders of a multi-cylinder engine having at least two cylinders is shown. Herein, the valve is the intake valve or the exhaust valve.

The first cam portion 40 includes a first low cam 41, a first normal cam 42, a second low cam 48, a second normal cam 49, and a first connecting portion 45.

The first normal cam 42 and second normal cam 49 may be formed in a general cam shape that an exterior circumference of a cut-plane is formed in an oval shape such that one end thereof is relatively further protruded to compare with the other end thereof. Typically, the one end of the cam is called “cam lobe”, and the other end of the cam is called “cam base”.

The cam base is a base circle of a cam, a part of an external circumference of the cam, which is formed in an arc shape having uniform radius. In addition, the cam lobe is a part of an external circumference of the cam 41, 42, 48, and 49 which pushes the valve opening/closing unit 5 from when opening of the valve is started to when closing of the valve is ended by rotation of the cam 41, 42, 48, and 49. Herein, the valve opening/closing unit 5 is a device that one end thereof is rolling-contacted with the cams 41, 42, 48, and 49 so as to be operated to open/close the valves by the rotation of the cams 41, 42, 48, and 49. The valve opening/closing unit 5 is well-known to a person of an ordinary skill in the art such that a detailed description thereof will be omitted.

The first low cam 41 and the first normal cam 42 are formed to be close with each other, and the second low cam 48 and the second normal cam 49 are formed to be close with each other. In addition, the first low cam 41 and the first normal cam 42 are paired with each other so as to operate one valve, and the second low cam 48 and the second normal cam 49 are paired with each other so as to operate the other valve.

The first connecting portion 45 connects the pair of the first low cam 41 and the first normal cam 42 with the pair of the second low cam 48 and the second normal cam 49. That is, the first connecting portion 45 is disposed between the pair of the first low cam 41 and the first normal cam 42 and the pair of the second low cam 48 and the second normal cam 49, and the first cam portion 40 is monolithically molded.

Meanwhile, the cam lobes of the first and second normal cams 42 and 49 may be further protruded from an exterior circumference of the camshaft 100 to compare with the cam lobes of the first and second low cams 41 and 48. In addition, the cam lobes of the first normal cam 42 and second normal cam 49 may be formed such that an engine has regular intake or exhaust timing that is predetermined by a person of an ordinary skill in the art. Herein, the valve lift for realizing the regular intake or exhaust timing predetermined by a person of an ordinary skill in the art will be called “normal lift”. Furthermore, the cam lobes of the first low cam 41 and the second low cam 41 are formed such that time from when opening of the valve is started to when closing of the valve is ended by rotation of the first low cam 41 and the second low cam 41 is relatively long to compare with the first normal cam 42 and second normal cam 49 and the first low cam 41 and the second low cam 41 realize the relative low valve lift to compare with the first normal cam 42 and second normal cam 49.

Therefore, the normal lift of the valve is realized when the valve opening/closing unit 5 is connected with the normal cam 42 and 49 so as to rolling-contact with the normal cam 42 and 49, and the low lift of the valve that open time thereof is increased is realized when the valve opening/closing unit 5 is connected with the low cam 41 and 48 so as to rolling-contact with the low cam 41 and 48. Furthermore, the first and second normal cams 42 and 49 or the first and second low cams 41 and 48 for operating the valve are selected according to the first cam portion 40 moves along an axial direction of the camshaft 100.

The second cam portion 60 includes a third low cam 61, a third normal cam 62, a fourth low cam 68, a fourth normal cam 69, and a second connecting portion 65.

Herein, the descriptions regarding the third low cam 61, the third normal cam 62, the fourth low cam 68, the fourth normal cam 69, and the second connecting portion 65 are respectively corresponded to the descriptions regarding the first low cam 41, the first normal cam 42, the second low cam 48, the second normal cam 49, and the first connecting portion 45, and thus will be omitted.

The solenoid 10 is provided so as to transform the rotation motion of the camshaft 100 to the rectilinear motion of the first cam portion 40 or the second cam portion 60. That is, the first cam portion 40 or the second cam portion 60 is rectilinearly moved along an axial direction of the camshaft 100 according to the rotation motion of the camshaft 100 if the solenoid 10 is operated. Herein, the solenoid 10 operated to on or off by an electrical control the solenoid 10 is well-known to a person of an ordinary skill in the art such that a detailed description thereof will be omitted.

The operating unit 30 and 50 is formed in a cylinder shape having a hollow like to the first and second cam portions 40 and 60, and the camshaft 100 is inserted into the hollow of the operating unit 30 and 50 such that the operating unit 30 and 50 is disposed on an exterior circumference of the camshaft 100. In addition, the hollow of the operating unit 30 and 50 may be formed that an internal circumference of the operating unit 30 and 50 is corresponded with an external circumference of the camshaft 100. Further, an external circumference of the operating unit 30 and 50 is formed in a circle shape having uniform radius. Furthermore, an interior circumference of the operating unit 30 and 50 is slid on an exterior circumference of the camshaft 100 such that the operating unit 30 and 50 is moved along an axial direction of the camshaft 100, and the operating unit 30 and 50 is adapted to rotate together with the camshaft 100.

The solenoid 10 includes a low lift solenoid 12 and a normal lift solenoid 14, and the operating unit 30 and 50 includes a low lift operating unit 30 and a normal lift operating unit 50.

The low lift operating unit 30 is integrally formed with the first cam portion 40 or is adapted to move together with the first cam portion 40. In addition, the low lift operating unit 30 rotating together with the camshaft 100 is moved in one direction along an axial direction of the camshaft 100 according to the operation of the low lift solenoid 12. Thus, the low lift that open time of the valve is relatively increased to compare with the normal lift. While it is shown that the low lift operating unit 30 is disposed at one end of the first low cam 41 in FIG. 1, it is not limited thereto in the disclosed embodiment.

For better comprehension and convenience of description, a forward direction will be defined a word as the one direction that the low lift operating unit 30 is moved for realizing the low lift of the valve and a reverse direction will be defined a word as an opposite direction of the forward direction.

The normal lift operating unit 50 is integrally formed with the second cam portion 60 or adapted to move together with the second cam portion 60. In addition, the normal lift operating unit 50 rotating together with the camshaft 100 is moved in the other direction along an axial direction of the camshaft 100 according to the operation of the normal lift solenoid 14. Thus, the normal lift of the valve is realized. While it is shown that the normal lift operating unit 50 is disposed at one end of the third normal cam 62 in FIG. 1, it is not limited thereto in the disclosed embodiment.

The interlock unit 70 is formed in a cylinder shape having a hollow like to the operating units 30 and 50 and the first and second cam portions 40 and 60, and the camshaft 100 is inserted into the hollow of the interlock unit 70 such that the interlock unit 70 is disposed on an exterior circumference of the camshaft 100. In addition, the hollow of the interlock unit 70 may be formed that an internal circumference of the interlock unit 70 is corresponded with an external circumference of the camshaft 100. Further, an external circumference of the interlock unit 70 is formed in a circle shape having uniform radius. Furthermore, an interior circumference of the interlock unit 70 is slid on an exterior circumference of the camshaft 100 such that the interlock unit 70 is moved along an axial direction of the camshaft 100, and the interlock unit 70 is adapted to rotate together with the camshaft 100.

The interlock unit 70 is disposed between the integrally formed first cam portion 40 and the integrally formed second cam portion 60. In addition, the interlock unit 70 performs a function that the first cam portion 40 and the second cam portion 60 are interlocked with each other.

The interlock unit 70 is operated to move in the forward direction if the low lift operating unit 30 moves in the forward direction. In addition, the integrally formed second cam portion 60 is pushed by the interlock unit 70 according to the interlock unit 70 is moved in the forward direction. Thus, the second cam portion 60 is moved in the forward direction.

The interlock unit 70 is operated to move in the reverse direction if the normal lift operating unit 50 moves in the reverse direction. In addition, the integrally formed first cam portion 40 is pushed by the interlock unit 70 according to the interlock unit 70 is moved in the reverse direction. Thus, the first cam portion 40 is moved in the reverse direction.

The pin operating unit 20 is provided for moving the interlock unit 70 along an axial direction of the camshaft 100. In addition, the pin operating unit 20 includes a housing 21, a hinge unit 22, a first pin 24, a second pin 25, and a pin fixing unit 27.

The housing 21 is a body of the pin operating unit 20 that the hinge unit 22, the first pin 24, the second pin 25, and the pin fixing unit 27 are mounted thereat.

The hinge unit 22 is adapted to perform hinge motion around a hinge shaft 23 mounted to the housing 21.

The first pin 24 and second pin 25 may be formed in a bar shape which is extended along one direction.

The first pin 24 is pushed by the hinge unit 22 according to the hinge motion of the hinge unit 22 such that the first pin 24 moves toward a direction to be protruded from the housing 21. In addition, the hinge unit 22 is pushed by the first pin 24 according to the first pin 24 is to be positioned at its original position such that the hinge unit 22 performs the opposite hinge motion. Further, the second pin 24 is pushed by the hinge unit 22 according to the hinge unit 22 performs the opposite hinge motion such that the second pin 25 moves toward a direction to be protruded from the housing 21. That is, the pin operating unit 20 is operated to interlock the first and second pins 24 and 25 with each other such that if one of the first pin 24 and the second pin 25 is to be positioned at original position to be not protruded from the housing 21, the other of the first pin 24 and the second pin 25 is to be protruded from the housing 21.

The pin fixing unit 27 is provided for fixing the pin positioned at original position of the first and second pin 24 and 25. A hooking groove 29 is formed at the first and second pin 24 and 25 for hooking the pin fixing unit 27 on the state that the first pin 24 or second pin 25 is positioned at original position, and the pin fixing unit 27 performs reciprocating motion between the first pin 24 and the second pin 25 such that a part of the pin fixing unit 27 is seated at the hooking groove 29 for fixing the pin positioned at original position of the first pin 24 and the second pin 25.

The pin fixing unit 27 is operated by a spring 28. In addition, the pin fixing unit 27 is seated at the hooking groove 29 formed at the one of the first and second pins 24 and 25 by relatively small force generated by pushing of the spring 28 and is escaped from the hooking groove 29 by relatively strong force generated by operation of the first and second pins 24 and 25. The hooking groove 29 and the part of pin fixing unit 27 contacted with the hooking groove 29 may be formed in a gradually curved surface such that the operation is easily performed.

The low lift operating unit 30, the normal lift operating unit 50, and the interlock unit 70 include the guide rail 32, 52, and 72.

The guide rail 72 of the interlock unit 70 is formed to be contacted with the first pin 24 or the second pin 25 protruded from the housing 21 by the operation of the pin fixing unit 27 and guide motion of the interlock unit 70. That is, when the camshaft 100 rotates on the state that the first pin 24 or second pin 25 is inserted into the guide rail 72 of the interlock unit 70, the interlock unit 70 is moved along an axial direction of the camshaft 100 according to the guide rail 72 guides relative movement of the first pin 24 or second pin 25 with the rotation of the interlock unit 70 that the first pin 24 or second pin 25 is moved along an exterior circumference of the interlock unit 70.

The low lift solenoid 12 includes a connecting pin 16 protruded by a bar shape, and the connecting pin 16 is contacted with the guide rail 32 of the low lift operating unit 30 according the operation of the low lift solenoid 12. In addition, the guide rail 32 of the low lift operating unit 30 is formed to contact with the connecting pin 16 and guide the motion of the low lift operating unit 30. That is, when the camshaft 100 rotates on the state that the connecting pin 16 is inserted into the guide rail 32 of the low lift operating unit 30, the low lift operating unit 30 is moved in the forward direction along an axial direction of the camshaft 100 according to the guide rail 32 guides relative movement of the connecting pin 16 with the rotation of the low lift operating unit 30 that the connecting pin 16 is moved along an exterior circumference of the low lift operating unit 30.

The normal lift solenoid 14 includes a connecting pin 18 protruded by a bar shape, and the connecting pin 18 is contacted with the guide rail 52 of the normal lift operating unit 50 according to the operation of the normal lift solenoid 14. In addition, the guide rail 52 of the normal lift operating unit 50 is formed to contact with the connecting pin 18 and guide the motion of the normal lift operating unit 50. That is, when the camshaft 100 rotates on the state that the connecting pin 18 is inserted into the guide rail 52 of the normal lift operating unit 50, the normal lift operating unit 50 is moved in the reverse direction along an axial direction of the camshaft 100 according to the guide rail 52 guides relative movement of the connecting pin 18 with the rotation of the normal lift operating unit 50 that the connecting pin 18 is moved along an exterior circumference of the normal lift operating unit 50.

The guide rails 32, 52, and 72 may be formed in a groove shape recessed from the exterior circumferences of the operating units 30 and 50 and the interlock unit 70. In addition, the groove shape guide rails 32, 52, and 72 are longitudinally formed along a circumferential direction of the operating units 30 and 50 and the interlock unit 70.

Furthermore, the guide rails 32, 52, and 72 are formed in a slanted shape as a set slope with reference to an axial direction of the camshaft 100 on an exterior circumference of the operating unit 30 and 50 or the interlock unit 70 such that the operating unit 30 and 50 and the interlock unit 70 are moved in one direction along an axial direction of the camshaft 100.

The first cam portion 40, the interlock unit 70, and the second cam portion 60 are sequentially moved in the forward direction by the rotation of camshaft 100 according to the shape of the guide rail 32, 52, and 72. The successive motion is for minimizing interference between the cam portion 40 and 60 and the valve according to the change of the valve lift is performed by on the state that the cam base is contacted with the valve.

The low lift operating unit 30 and the first cam portion 40 is integrally moved toward the forward direction when the connecting pin 16 is moved along the guide rail 32 by the rotation of the low lift operating unit 30. In addition, the first cam portion 40 moves in the forward direction and pushes the interlock unit 70 as a set distance toward the forward direction.

The interlock unit 70 is moved toward the forward direction according to the first pin 24 is moved along the guide rail 72 by rotation of the interlock unit 70 pushed as the set distance in the forward direction. In addition, the interlock unit 70 is contacted with the second cam portion 60, and pushes the second cam portion 60 toward the forward direction such that the second cam portion 60 is moved in the forward direction.

Meanwhile, at least one of gap between the first cam portion 40 and the interlock unit 70 and between the second cam portion 60 and the interlock unit 70 is to be always disposed apart from each other. The disposing apart is for sequentially moving the first cam portion 40, the interlock unit 70, and the second cam portion 60 according to the interlock unit 70 is moved between the first cam portion 40 and the second cam portion 60. In addition, the timings for changing the valve lifts of the cylinder which at the first cam portion 40 is disposed and the cylinder which at the second cam portion 60 is disposed are determined according to the disposing apart and the shape of the guide rails 32, 52, and 72. Further, the distance, that the interlock unit 70 moves along an axial direction, determined by the shape of the guide rail 72 is longer than the distance, that the low lift operating unit 30 moves along an axial direction, determined by the shape of the guide rail 32.

The successive motions toward the reverse direction of the second cam portion 60, the interlock unit 70, and the first cam portion 40 are started according to the connecting pin 18 of the normal lift solenoid 14 is inserted into the guide rail 52 of the normal lift operating unit 50 with reference to the valve timing of the cylinder which at the second cam portion 60 is disposed, on the contrary to the successive motions toward the forward direction of the first cam portion 40, the interlock unit 70, and the second cam portion 60.

The second cam portion 60, the interlock unit 70, and the first cam portion 40 are sequentially moved in the reverse direction by the rotation of camshaft 100 according to the shape of the guide rail 32, 52, and 72. The successive motion is for minimizing interference between the cam portion 40 and 60 and the valve according to the change of the valve lift is performed by on the state that the cam base is contacted with the valve.

The normal lift operating unit 50 and the second cam portion 60 is integrally moved toward the reverse direction when the connecting pin 18 is moved along the guide rail 52 by the rotation of the normal lift operating unit 50. In addition, the second cam portion 60 moves in the reverse direction and pushes the interlock unit 70 as a set distance toward the reverse direction.

The interlock unit 70 is moved toward the reverse direction reverse direction the second pin 25 is moved along the guide rail 72 by rotation of the interlock unit 70 pushed as the set distance in the reverse direction. In addition, the interlock unit 70 is contacted with the first cam portion 40, and pushes the first cam portion 40 toward the reverse direction such that the first cam portion 40 is moved in reverse direction.

Meanwhile, the distance, that the interlock unit 70 moves along an axial direction, determined by the shape of the guide rail 72 is longer than the distance, that the normal lift operating unit 50 moves along an axial direction, determined by the shape of the guide rail 52.

The multiple variable valve lift apparatus 1 may be applied to an in-line four or more than four cylinder engine for operating valves respectively disposed at cylinders by equal to or more than four according to constituent elements such as the first and second cam portions 40 and 60 and the interlock unit 70 are further disposed thereat by the same type.

The multiple variable valve lift apparatus 1 applied to an in-line four or more than four cylinder engine is operated by only the two solenoids 12 and 14 too. In addition, the operation of the multiple variable valve lift apparatus 1 is started by the motion along axial direction of the one cam portion, and is performed according to the interlock units 70 and the cam portions are sequentially and alternately moved toward one direction.

According to the multiple variable valve lift apparatus 1, the composition can be simple and the operations can be simultaneously efficient by the pin operating unit 20 and the interlock unit 70 moving along axial direction of the camshaft 100 by the operation of the pin operating unit 20. In addition, interference between constituent elements can prevented as the cam portions 40 and 60 disposed at each cylinder are operated step by step by the interlock unit 70. Furthermore, spatial utility can be improved and cost can be simultaneously reduced as a number of the solenoids 10 are to be minimized.

Meanwhile, It is not limited that the normal cams 42, 49, 62, and 69 realizing the normal lift and the low cams 41, 48, 61, and 68 realizing the low lift having the open time of the valve which is relatively longer to compare with the normal lift are the multiple variable valve lift apparatus 1 according to an exemplary embodiment of the present invention, and the normal cams 42, 49, 62, and 69 and the low cams 41, 48, 61, and 68 can be applied to the all multiple variable valve lift apparatus that the cam rolling-contacting with the valve opening/closing unit 5 is selected for changing the valve lift.

FIG. 2 is a perspective view of a cam portion according to an exemplary embodiment of the present invention. In addition, the first cam portion 40 is shown in FIG. 2.

Hereinafter, the cam portions 40 and 60 forming the low cams 41, 48, 61, and 68 and the normal cams 42, 49, 62, and 69 will be described in detail based on the first cam portion 40 shown in FIG. 2. That is, the first cam portion 40 will be representatively described about the cam portions 40 and 60 which may be additionally provided to the multiple variable valve lift apparatus 1.

As shown in FIG. 2, a spline 44 is formed on an interior circumference of the cam portion 40 and 60, and the low cams 41, 48, 61, and 68 and the normal cams 42, 49, 62, and 69 are formed on an exterior circumference of the cam portion 40 and 60, and the cam portion 40 and 60 may be integrally formed with the operating unit 30 and 50.

The cam lobes of the low cams 41, 48, 61, and 68 are formed along external circumferences of the cam portion 40 and 60 on relatively wider range to compare with the cam lobes of the normal cams 42, 49, 62, and 69. Therefore, the time from when opening of the valve is started to when closing of the valve is ended by the rotation of the low cams 41, 48, 61, and 68 is longer than the time from when opening of the valve is started to when closing of the valve is ended by the rotation of normal cams 42, 49, 62, and 69.

Herein, in case that the intake valve is opened/closed by the low cams 41, 48, 61, and 68, amount of effective air remained in the combustion chamber may be decreased and power loss of a piston performing reciprocal motion in a cylinder of an engine may be minimized according to air flowed into a combustion chamber in the low speed low load of an engine flows backward through an intake hole of an engine.

the operation for increasing the open time of the intake valve and for doing that the close timing the valve is later than a close timing of the valve by the normal cams 42, 49, 62, and 69 is called “late intake valve close (LIVC)”, and the cam realizing the valve lift of the operation is called “LIVC cam”, and the LIVC and LIVC cam are well known to a person of an ordinary skill in the art.

Meanwhile, the low cams 41, 48, 61, and 68 which are the LIVC cam according to an exemplary embodiment of the present invention are adapted to realize the valve lift which is lower than the normal lift. According to the low cams 41, 48, 61, and 68, mechanical friction may be decreased and fuel consumption may be improved to compare with case that the LIVC cam realizes the valve lift which is higher than the normal lift.

Hereinafter, it will be defined that the low cams 41, 48, 61, and 68 according to an exemplary embodiment of the present invention have same mean with the LIVC cam. In addition, the valve lift realized by the LIVC cams 41, 48, 61, and 68 will be called “LIVC lift”.

FIG. 3 is a graph showing valve lift by a normal cam and a LIVC cam according to an exemplary embodiment of the present invention.

In FIG. 3, horizontal axis is time of valve lift, and vertical axis is size of valve lift. In addition, a curved line C1 illustrated by a dotted line represents the normal lift, a curved line C2 illustrated by a solid line represents the LIVC lift.

As shown in FIG. 3, size L2 of the LIVC lift by the LIVC cams 41, 48, 61, and 68 is smaller than size L1 of the normal lift by the normal cams 42, 49, 62, and 69. In addition, time of the LIVC lift by the LIVC cams 41, 48, 61, and 68 is longer than by time of the normal lift the normal cams 42, 49, 62, and 69. Meanwhile, shapes of the LIVC cams 41, 48, 61, and 68 is changed and applied by a person of an ordinary skill in the art such that size L2 of the LIVC lift is smaller than size L1 of normal lift and time of the LIVC lift is longer than time of the normal lift.

According to an exemplary embodiment of the present invention, required torque of the cam can be minimized as the LIVC lift is realized by the low lift to compare with the normal lift, and noise and vibration generated in an engine can be minimized as drive impact of the valve is reduced. In addition, the velocity of the intake air flowed into an engine may become fast, and combust stability may be ensured, and fuel consumption can be improved as the LIVC lift is realized by the low lift to compare with the normal lift. Furthermore, the valve overlap time that open times of the intake valves are overlapped with each other is maximized according to design freedom about open timing of the intake valve can be improved.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A multiple variable valve lift apparatus connected with a valve opening and closing unit which is adapted to rolling-contact one end thereof with a cam and is operated to open or close by a rotation of the cam, and operating to select the cam which is rolling-contacted with the valve opening and closing unit for changing a valve lift, the multiple variable valve lift apparatus comprising: a normal cam rolling-contacting with the valve opening and closing unit so as to realize a normal lift of a predetermined valve; and a low cam rolling-contacting with the valve opening and closing unit so as to realize a valve lift which is lower and longer than the normal lift realized by the normal cam; wherein the normal cam or the low cam is selectively rolling-contacted to the valve opening/closing unit according to a driving state.
 2. The apparatus of claim 1, wherein the valve is early opened and is lately closed to compare with the normal lift in the valve lift realized by the low cam.
 3. The apparatus of claim 1, wherein the normal lift realized by that the normal cam is rolling-contacted with the valve opening and closing unit is a predetermined valve lift such that efficiency of an engine is improved when a vehicle is driven at a high speed and a normal speed.
 4. The apparatus of claim 3, wherein the low cam realizes the valve lift by rolling-contacting with the valve opening and closing unit such that efficiency of an engine is improved when a vehicle is driven at a low speed. 